This report shows that all the analysed acid volcanics of the Rehoboth Basement Inlier are high-K rhyolites of mostly peraluminous nature. According to their element distribution patterns they may represent more evolved Gamsberg-, Piksteel- and Weener-type magmas. Post-genetic K-metasomatic processes are indicated by high K2 O/Na2 O ratios of the analysed specimens. A Rb/Sr isochron for rhyolites of the Nückopf Formation yielded an age of 948.0 ± 24.7 Ma. U/Pb dating on zircons from rhyolite dykes crosscutting the MarienhofFonnation yielded an age of 1210 ± 7 Ma.